1. Field of the Invention
The instant invention relates to a telephone lead-in cable SVDL type (voice, video, data, and lead-in) permitting the connection of the users to the public telephone system with a high speed digital services link, besides the analog services currently offered. This is obtained through the integration of a balanced circuit to the original design of two parallel metal elements also serving as self-supporting elements.
2. Description of the Prior Art
Generally, the air lead-ins of unitary telephone services have been limited with regard to bandwidth and radio-interference resistance because of their design. The demand for transmission means capable of supporting a bandwidth large enough to meet the growing demand for digital services in the coming years also requires designs that do not increase the cost or limit the installation ease of the current products. Besides, in the case of cables used for the connection of users to the telephone network, the design is a decisive factor. The cable must be light and economical, must be capable of allowing data transmission and speeds higher than 155 Mbps, but must also present an acceptable response in frequencies over 100 MHz and support its own weight in spans of more than 100 meters. The cable must also be weather resistant and, in windy and icy conditions, the design must allow for reinforcement without having to change its shape, in such a way that the same anchor elements can be used in this type of services.
Among the known techniques to overcome the above mentioned problems, U.S. Pat. No. 4,467,138 describes a xe2x80x9clead cable for plural communicationxe2x80x9d the design of which is related to a flat construction communication conductor having two or more communication ports, polyolefin insulated cables, assembled lengthwise, placed in groups on opposite sides and parallel to a conductive steel wire.
Even though cables presenting twisted pair conductors are known, not all them have the same application, i.e. according to the use, the design and even the number of lays of the twisted pair vary on a case per case basis. For example, U.S. Pat. No. 6,064,008, describes a communication cable having two pairs of twisted conductors, the main characteristic of which is not the twisted pairs but the insulating filing material based on a fluorinated polymer with a blowing agent.
The applicant has developed a SVDL type lead-in cable the novel characteristic of which is that its design permits two transmission circuits using one of them as self-supporting element for air lead-ins and voice signal transmission; the other circuit permitting, if necessary, to have a service dedicated to high speed digital signal transmission without interfering in any way with the voice service signals or having to use additional electronic circuit to separate the signals. The design is also highly near end crosstalk (NEXT) resistant between the two circuits.